Electrocution (large quantities of charge flow through the body to earth) Insulating mats or shoes

Transcription

1 P4 in 30 minutes

2 P4a: Sparks Like charges repel and unlike charges attract. a positive charge due to lack of electrons a negative charge due to an excess of electrons. Atoms or molecules that have become charged are ions.

3 Explain how static electricity can be dangerous: Explosions eg flammable gases or vapours or with high concentrations of oxygen Correct earthing (bond fuel tanker to aircraft) Electrocution (large quantities of charge flow through the body to earth) Insulating mats or shoes

4 Explain how static electricity can be a nuisance: Dust Static cling Anti-static sprays

5 P4b: Uses of electrostatics Electrostatic dust precipitators remove smoke particles from chimneys: high voltage metal grids put into chimneys to produce a charge on the dust dust particles gain or lose electrons and become charged dust particles induce a charge on the earthed metal plate dust particles are attracted to the plates plates struck and dust falls to collector.

6 Paint spraying: spray gun charged paint particles charged the same so repel giving a fine spray object charged oppositely to paint so attracts paint even coat with less waste.

7 Defibrillator: paddles charged good electrical contact with patient s chest charge passed through patient to make heart contract care taken not to shock operator.

8 P4c: Safe electricals Variable resistors longer wires have more resistance thinner wires have more resistance

9 Mains wires live carries the high voltage neutral completes the circuit earth a safety wire to stop the appliance becoming live. Double insulated insulating case, no earth wire

10 Fuse Too large a current causes the fuse to melt preventing flow of current prevents flex overheating and causing fire prevents further damage to appliance.

11 power = voltage current (W) (V) (A) Use this equation to calculate the current. Choose the fuse with the next highest value Eg 700 W, 230 V gives current of 3.04 A Use 5 A fuse.

12 P4d: Ultrasound Longitudinal waves: wavelength frequency compression (a region of higher pressure) rarefaction (a region of lower pressure). amplitude.

13 Longitudinal - parallel Transverse - perpendicular

14 Frequency of ultrasound is higher than the upper threshold of human hearing (20000Hz) Medical treatment break down kidney and other stones Medical diagnosis body scans from reflected ultrasound Better than X-rays because: images of soft tissue non-ionising - does not damage living cells.

15 P4e: What is radioactivity? From the nucleus of an atom that is unstable. alpha, beta and gamma.

16 Half-life.

17 Ionisation gain or removal of electrons from particles Alpha particles are good ionisers. Alpha particle - helium nucleus. Beta particle - fast moving electron.

18 Nuclear changes When an alpha particle is emitted: Neutrons -2, Protons -2 mass number decreases by 4 atomic number decreases by 2 new element formed.

19 Nuclear changes When a beta particle is emitted: Neutrons -1, Protons +1 mass number is unchanged atomic number increases by one new element formed.

20 P4f: Uses of radioisotopes Background radiation some from waste products and man-made sources eg waste from industry, hospitals. Relative significance?

21 Tracers Gamma emitter put into pipe progress tracked with detector leak/blockage shown by reduction/no radioactivity after the point of blockage

22 Smoke detector smoke particles hit by alpha radiation less ionisation of air particles current is reduced causing alarm to sound.

23 Dating of rocks eg. uranium/lead ratio. Carbon dating % Carbon-14 in the air has not changed for thousands of years Death stops taking in carbon Carbon-14 in the wood decays and activity decreases

24 P4g: Treatment X-rays Absorption of X-rays depends on the thickness and density of the materials.

25 Gamma rays - given out from the nucleus of certain radioactive materials X-rays made by firing high speed electrons at metal targets X-rays are easier to control than gamma rays

26 Tracers beta or gamma emitter (why?) with a short half life (why?) drunk/eaten/ingested/injected into the body allowed to spread through the body followed on the outside by a radiation detector.

27 Cancer treatment gamma rays focused on tumour wide beam used rotated round the patient with tumour at centre limiting damage to non-cancerous tissue.

28 P4h: Fission and fusion Nuclear power station: nuclear reaction heat, steam, turbine, generator

29 Fission reaction: uranium nucleus hit by neutron causes nucleus to split energy released more neutrons released. Materials can become radioactive as a result of absorbing extra neutrons

30 Chain reaction: when each uranium nucleus splits more than one neutron is given out - these neutrons can cause further uranium nuclei to split. Nuclear bomb - a chain reaction that has gone out of control. To stop nuclear reactions going out of control: rods placed in the reactor to absorb some of the neutrons enough neutrons to remain to keep the process operating.

31 Fusion two nuclei join together produces large amounts of heat energy in stars, fusion happens under extremely high temperatures and pressures fusion bombs are started with a fission reaction which creates exceptionally high temperatures for power generation exceptionally high temperatures and/or pressures are required and this combination offers safety and practical challenges.

32 Fusion power research is carried out as an international joint venture.

33 Cold fusion experiments and data have been shared between scientists. Cold fusion is still not accepted as a realistic method of energy production.

34 Good luck!